The problem of motion control of Wheeled Mobile Manipulators (WMMs) is extensively studied in past decade. Mobile manipulator refers to robotic system which is built by a robotic arm mounted on a mobile platform. This kind of system, combines the manipulability of a fixed base manipulator, with the moving wheeled platform, thus allowing the most usual missions of robotic systems which require both locomotion in large workspace and manipulation abilities. Mobile manipulators are often used for tasks such as assembly, iection, spray painting or part transfer. One of the most common mobile robots is the differential-drive type, which is a typical example of nonholonomic mechanisms. The assumption for pure wheels rotation (i.e., no slipping occurs) causes kinematic constraint of nonholonomic type to system. This constraint limits the instantaneous velocity of the platform to certain directions. Furthermore the coupled dynamic equations of the mobile platform and manipulator, along with performing task by avoiding obstacles, makes designing a precise controller for the mobile manipulator, very challenging. This thesis addresses the problem of end-point position tracking control of mobile manipulators operating in the task space. First a class of non-linear simple model-based task space regulator is proposed, then the different constraints regarding task in hand such as obstacle avoidance is introduced. Avoiding singular configurations are also considered by using manipulability index, it’s necesery to avoid these configurations and reaching the end-point with high manipulability. With the help of exterior penalty function approach, manipulability and obstacles avoidance inequality constraints are included in our novel control law. To show the efficiency of proposed approach, four simulations are carried out on a differential drive platform with a spatial manipulator of three kinematic pairs (RRR manipulator) and results are presented. Results show that propose approach can successfully track end-point position and avoid both obstacles and singular configurations Keyword: Mobile Manipulator, Nonholonomic Constraint, Obstacle Avoidance, Manipulability Index, Robust Control
